This invention is generally directed to novel squaraine compositions of matter, and the incorporation thereof into layered photoresponsive imaging members. More specifically, the present invention relates to layered photoresponsive imaging members having incorporated therein as photogenerating pigments specific novel fluorinated squaraine compounds. In one embodiment, the photoresponsive imaging member of the present invention is comprised of a photoconductive layer containing the novel fluorinated squaraine compounds illustrated herein, and an aryl amine hole transport layer. Also encompassed within the present invention are imaging members which are responsive to visible light, and infrared illumination needed for laser printing, which members can comprise, in addition to a hole transport layer, a photogenerating layer, and a photoconductive layer containing the novel fluorinated squaraine compounds illustrated herein. Accordingly, the aforementioned imaging members can function so as to enhance or reduce the intrinsic properties of a charge carrier photogenerating material contained therein in the infrared and/or visible range of the spectrum thereby allowing the member to be sensitive to either visible light and/or infrared wavelengths. Further, imaging members without the photogenerating layer are sensitive to either visible light, and/or infrared wavelengths.
Numerous different xerographic photoconductive members are known including, for example, a homogeneous layer of a single material such as vitreous selenium, or a composite layered device with a dispersion of a photoconductive composition. An example of one type of composite xerographic photoconductive member is described in U.S. Pat. No. 3,121,006 wherein there is disclosed finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. These members comprise coated on a paper backing a binder layer containing particles of zinc oxide uniformly dispersed therein. The binder materials disclosed in this patent include polycarbonate resins, polyester resins, and polyamide resins, which resins are incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles. Accordingly, as a result the photoconductive particles must be in a substantially contiguous particle to particle contact throughout the layer for the purpose of permitting charge dissipation required for a cyclic operation.
There are also known photoreceptor members comprised of inorganic or organic substances wherein the charge carrier generating, and charge carrier transport functions are accomplished by discrete contiguous layers. Additionally, layered photoreceptor devices are disclosed in the prior art which include an overcoating of an electrically insulating polymeric material. However, the art of xerography continues to advance and there is desired other layered photoresponsive devices which are responsive to visible light, and/or infrared illumination.
Recently, there has been disclosed layered photoresponsive devices comprised of separate generating layers, and transport layers, reference U.S. Pat. No. 4,265,990; and overcoated photoresponsive materials with a hole injecting layer, reference U.S. Pat. No. 4,251,612. Examples of photogenerating layers disclosed in these patents are trigonal selenium, and phthalocyanines, while examples of transport layer molecules include the aryl amine diamines as mentioned herein. The disclosures of each of the aforementioned U.S. Pat. Nos. 4,265,990 and 4,251,612 are totally incorporated herein by reference.
Many other patents are in existence that describe layered photoresponsive devices with generating pigments, such as U.S. Pat. No. 3,041,167, which discloses an overcoated imaging member containing a conductive substrate, a photoconductive layer, and an overcoating layer of an electrically insulating polymeric material. This member is utilized in an electrophotographic copying method by, for example, initially charging the layered device with an electrostatic charge of a first polarity, and imagewise exposing to form an electrostatic latent image which can be subsequently developed. Prior to each succeeding imaging cycle, the imaging member can be charged with an electrostatic charge of a second opposite polarity. Sufficient additional charges of the second polarity are applied so as to create across the member a net electrical field of the second polarity. Simultaneously, mobile charges of the first polarity are created in the photoconductive layer by applying an electrical potential to the conductive substrate. The imaging potential which is developed is present across the photoconductive layer and the overcoating layer.
There is also disclosed in Belgian Pat. No. 763,540 an electrophotographic member having at least two electrically operative layers. One of these layers is comprised of a photoconductive substance which is capable of photogenerating charge carriers, and injecting the carriers into a continuous active layer containing an organic transporting material which is substantially non-absorbing in the spectral region of intended use. Additionally, there is disclosed in U.S. Pat. No. 3,041,116 a photoconductive device containing a transparent plastic material overcoated on a layer of vitreous selenium present on a substrate.
Furthermore, there is disclosed in U.S. Pat. Nos. 4,232,102 and 4,233,383, photoresponsive imaging members comprised of trigonal selenium doped with sodium carbonate, sodium selenite, and trigonal selenium doped with barium carbonate, and barium selenite or mixtures thereof. Moreover, there is disclosed in U.S. Pat. No. 3,824,099 certain photosensitive hydroxy squaraine compositions. According to the disclosure of this patent, the squaraine compositions are photosensitive in normal electrostatographic imaging systems.
Also, there is disclosed in U.S. Pat. No. 4,415,639 the use of hydroxy squaraines as a photoconductive compound in an infrared sensitive photoresponsive device. More specifically, there is described in this patent an improved photoresponsive device with a substrate, a hole blocking layer, an optional adhesive interfacial layer, an inorganic photogenerating layer, a photoconductive composition capable of enhancing or reducing the intrinsic properties of the photogenerating layer, which photoconductive composition is selected from various squaraine compositions, including hydroxy squaraine compositions, and a hole transport layer.
Additionally, there is illustrated in U.S. Pat. No. 4,471,041, the disclosure of which is totally incorporated herein by reference, the use of novel julolidinyl squaraine compositions, such as bis-9-(8-hydroxyjulolidinyl)squaraine, as photoconductive substances in photoresponsive devices which are sensitive either to infrared light, and/or visible illumination. It is indicated in this patent that the improved photoresponsive device in one embodiment is comprised of a supporting substrate, a hole blocking layer, an optional adhesive interfacial layer, an inorganic photogenerating layer, a photoconducting composition capable of enhancing or reducing the intrinsic properties of the photogenerating layer, which composition is comprised of the novel julolidinyl squaraine compositions disclosed therein, and a hole transport layer.
There is further disclosed in U.S. Pat. No. 4,486,520, the disclosure of which is totally incorporated herein by reference, photoresponsive imaging members with photogenerating layers of certain novel fluorinated squaraine compositions. Examples of specific fluorinated squaraines disclosed include bis(4-dimethylamine-2-fluorophenyl)squaraine, bis(4-[N,N,diethylamino-2-fluorophenyl])squaraine, bis(4-[N-methyl-N-ethyl-2-fluoroaniline])squaraine, bis(4-[N,N-dibenzyl-2-fluoroaniline])squaraine, bis(4-[N-methyl-N-benzyl-2-fluoroaniline])squaraine, bis(4-[N-ethyl-N-benzyl-2-fluoroaniline])squaraine, and the like. Other useful fluorinated squaraine compositions include bis(4-[N,N,-di(4-chlorophenylmethyl)-2-fluorophenyl])squaraine, bis(4-[N-methyl-N-(4-chlorophenylmethyl)-2-fluorophenyl])squaraine, and bis(4-[N-benzyl-N-(-chlorophenylmethyl)-2-fluorophenyl])squaraine. While the squaraines of the present invention are similar to those as disclosed in the aforementioned patent, they differ in a number of significant respects, particularly for example the squaraine compounds of the present invention have present on each of the benzene rings attached to the squaric acid moiety, in addition to fluorine atoms at specific positions, various organic groups as disclosed herein. Moreover, the fluorinated squaraine compounds of the present invention are of superior xerographic performance in comparison to those as described in the '520 patent. The squaraine compounds of the present invention also possess, in many instances, different spectral response, dark decay properties, and physical characteristics, inclusive of solubility parameters, than those squaraines of the above patent.
Therefore, while numerous squaraine compositions are known, there continues to be a need for novel squaraine compositions, particularly squaraine compositions of superior photosensitivity. Additionally, there continues to be a need for photoresponsive imaging members containing as a photoconductive layer highly sensitive fluorinated squaraine compositions of matter. Further, there continues to be a need for novel fluorinated squaraine compounds which when selected for layered photoresponsive imaging members allow for the generation of acceptable images, which members can also be repeatedly used in a number of imaging cycles without deterioration thereof from the machine environment or surrounding conditions. Moreover, there continues to be a need for improved layered imaging members with certain fluorinated photogenerating pigments which are substantially inert to the users of such members. Furthermore, there continues to be a need for overcoated photoresponsive imaging members which are sensitive to a broad range of wavelengths; and more specifically, are sensitive to infrared light and visible light thereby permitting their use in a number of imaging and printing systems. There is also a need for new specific fluorinated squaraine photogenerating pigments which simultaneously possess high photosensitivity, low dark decay properties, and high charge acceptance values.